Wasm-pack: Allow skipping `.gitignore` generation

[RReverser]

💡 Feature description

Since implementing self-.gitignore generation in https://github.com/rustwasm/wasm-pack/issues/473, I've come across few codebases that prefer not to publish npm artifacts elsewhere nor integrate Rust build into their build process, but keep any artifacts in the Git repo.

I suggest adding --no-gitignore option for such usecases.

Alternative

Since in such cases module is not intended to be published anywhere, another alternative could be to implement this (omit .gitignore) as part of --no-pack implementation proposed here https://github.com/rustwasm/wasm-pack/issues/691.

cc @ashleygwilliams

[RReverser]

Actually... I realised that this is easily worked around by using one-off git add --force pkg/... and it's even better because you can selectively include only files you need in the repo (e.g. omit package.json or .d.ts).

[David-OConnor]

I still think this would be nice to have.

[olanod]

Same, I'd like to generate only the wasm and js and skip all the extra stuff since I'm not using npm